Arrhythmias – therapy

Question 1

What is the Vaughan-Williams classification of antiarrhythmic drugs?

Answer 1

A system classifying antiarrhythmic drugs based on their mechanism of action on ion channels and receptors.

Question 2

What are the four classes in the Vaughan-Williams classification?

Answer 2

🩺 Class I – Sodium (Na⁺) channel blockers (membrane stabilization)
🩺 Class II – Beta-blockers (reduce sympathetic stimulation)
🩺 Class III – Potassium (K⁺) channel blockers (prolong repolarization)
🩺 Class IV – Calcium (Ca²⁺) channel blockers (slow conduction)

Question 3

What are the Class I (Na⁺ channel blockers) subtypes and examples?

Answer 3

Class Ia – Moderate blockade → Prolongs AP duration (e.g., Quinidine, Procainamide)

Class Ib – Weak blockade → Shortens AP duration (e.g., Lidocaine, Mexiletine)

Class Ic – Strong blockade → Minimal AP effect but slows conduction (e.g., Flecainide, Propafenone)

Question 4

What are examples of Class II antiarrhythmics (Beta-blockers)?

Answer 4

🩸 Atenolol, Metoprolol, Propranolol, Esmolol
🔹 Reduce sympathetic stimulation
🔹 Slow AV node conduction (used in AF)
🔹 Decrease heart rate & contractility

Question 5

What are examples of Class III antiarrhythmics (K⁺ channel blockers)?

Answer 5

⚡ Amiodarone, Sotalol, Dofetilide, Ibutilide
🔹 Prolong repolarization (increase QT interval)
🔹 Used in AF, VT, VF
🔹 Amiodarone has side effects (lung, liver, thyroid toxicity)

Question 6

What are examples of Class IV antiarrhythmics (Ca²⁺ channel blockers)?

Answer 6

💊 Verapamil, Diltiazem
🔹 Block AV node conduction
🔹 Used in supraventricular tachycardias (SVT, AF)
🔹 Avoid in heart failure (negative inotropic effect)

Question 7

What is warfarin and how does it work?

Answer 7

Vitamin K antagonist

Inhibits clotting factors II, VII, IX, X

Requires INR monitoring (target 2-3 in AF)

Question 8

What are the downsides of warfarin?

Answer 8

⚠ Slow onset (needs bridging with heparin)
⚠ INR variability (requires monitoring)
⚠ Dietary interactions (Vitamin K-rich foods affect dosing)
⚠ Bleeding risk

Question 9

What are DOACs and why are they preferred over warfarin?

Answer 9

Direct Oral Anticoagulants (DOACs) include Apixaban, Rivaroxaban, Dabigatran

Advantages:
✅ No INR monitoring
✅ Fewer food interactions
✅ Faster onset

Question 10

What is the role of heparin in anticoagulation?

Answer 10

Unfractionated Heparin (UFH): Binds antithrombin, inhibits Factor Xa & IIa

Low Molecular Weight Heparin (LMWH) (e.g., Enoxaparin): More Factor Xa selective, better bioavailability

Question 11

Mnemonic for Vaughan-Williams Classification

Answer 11

📌 Some Block Potassium Channels

Sodium channel blockers (Class I)
Beta-blockers (Class II)
Potassium channel blockers (Class III)
Calcium channel blockers (Class IV)